The present invention relates to devices for obtaining a tissue biopsy sample, and more particularly to a device for obtaining a soft tissue core biopsy sample.
Clinicians obtain biopsy specimens for the purpose of diagnosing, staging and grading disease states. One type of biopsy device is a core biopsy needle, which typically operates by coaxial action of an inner needle or stylet having a specimen notch and an outer needle or cannula having a sharp end, with the tip of the inner stylet proud of the end of the outer cannula. The stylet is advanced so that the specimen notch is exposed to tissue, which prolapses into the notch. The cannula is then advanced over the stylet so that the sharp end of the cannula severs the tissue leaving the specimen in trapped within the notch. The volume of the specimen is limited by the notch and the inner diameter of the cannula.
In many biopsy situations, clinicians may desire a full, rounded core sample. The larger cross-section and volume of tissue can provide a more accurate assessment of the tissue pathology. It is also desirable to obtain full, clean core samples that have not been crushed by devices penetrating into tissue, since “crush artifacts” can compromise the analysis of the retrieved sample. In addition, the larger volume of the full core may often provide enough tissue so that only a single pass of the biopsy needle is required. Moreover, it may be desirable to obtain a core sample without having to penetrate past a desired depth of tissue in order to obtain a corresponding desired depth of core sample. It is preferable to insert a biopsy needle only as far as necessary to obtain the desired core sample. It is also desirable to maximize the amount of tissue obtained through the smallest diameter access into the patient.
Coring devices are well known for obtaining samples of hard tissue such as bone. These coring devices include an outer needle having a sharpened edge that is manually pushed and rotated into bone. In this case the rigidity of the tissue—e.g., bone—assures a generally intact full core sample. However, soft tissues do not have the same rigidity and are prone to flow away from the cutting needle. One known device capable of obtaining full core samples of soft tissues is the FNA (fine needle aspiration) device. This device typically includes an outer needle having a sharpened edge at the tip. The outer needle is typically manually moved back and forth while rotating the needle into the target tissue. The use of aspiration helps pull the tissue into the FNA needle. Obtaining core samples in this manner requires a certain amount of dexterity to “tease” the tissue into the needle. Thus, the success of the biopsy is typically technique dependent. Moreover, the FNA procedure takes time ensure that a suitable sample is obtained. In many cases, multiple attempts are required to obtain an adequate sample, which exposes the patient to further discomfort and pain.
Partially and fully automated biopsy devices simplify and shorten the biopsy procedure, but generally eliminate the ability to “tease” the tissue into the coring cannula or needle. While an FNA device may be advanced into soft tissue at a rate of 2 cm/m in, a typical automated biopsy device advances the outer needle into the tissue at a rate of 200 cm/min. At these speeds the coring needle has a tendency to push the tissue aside, rather than to draw the tissue into the needle. There is a continuing need for biopsy devices, and particularly full core biopsy devices, which can quickly and efficiently obtain large, intact tissue samples. The need is particularly acute for soft tissue samples because the soft tissue can be difficult to extract and retain without damage to the tissue.